Positively charged toners containing vinyl pyrrolidone polymers

Abstract

Disclosed is a positively charged toner composition comprised of a resin, a colorant and polymers of vinyl pyrrolidone of the formula: <IMAGE> wherein x is a number of from about 20 to 1,800 and y is zero, or 1. A developer material is typically formulated by adding a carrier to the toner composition. Images of high quality are obtained when using these developers in an electrophotographic imaging system. The polymers of vinyl pyrrolidone are also useful as dispersants.

What is claimed is: 
     
       1. A positively charged dry toner composition comprised of a resin, a colorant, a carrier, and polymers of vinyl pyrrolidone of the formula: ##STR3## wherein x is a number of from about 20 to 1,800 and y is zero, or 1. 
     
     
       2. A toner composition in accordance with claim 1 wherein y is zero, and the molecular weight of the polyvinyl pyrrolidone is from about 5,000 to about 300,000. 
     
     
       3. A toner composition in accordance with claim 1 wherein the polymer is a styrene/butyl methacrylate/vinyl pyrrolidone terpolymer, or a vinyl pyrrolidone/vinyl acetate copolymer. 
     
     
       4. A toner composition in accordance with claim 1 wherein the resin is styrene/n-butyl methacrylate, and the colorant is carbon black. 
     
     
       5. A toner in accordance with claim 1 wherein the polymer of vinyl pyrrolidone is coated on the colorant. 
     
     
       6. A toner in accordance with claim 1 wherein the carrier is steel, or a metal core coated with a fluoropolymer. 
     
     
       7. A method of imaging comprising forming an electrostatic latent image on a photoreceptor which is negatively charged, contacting the image with a positively charged dry developer comprising a resin material, a colorant, a carrier, and polymers of vinyl pyrrolidone of the formula: ##STR4## wherein x is a number of from about 20 to 1,800 and y is zero, or 1, subsequently transfferring the developed image to a substrate and permanently affixing the image thereto. 
     
     
       8. A method of imaging in accordance with claim 7 whereby y is zero, and the molecular weight of the polyvinyl pyrrolidone is from about 5,000 to about 300,000.